A sewage surveillance effort to track COVID-19

ANN ARBOR—Could a community’s wastewater give an early warning of the spread of COVID-19?

With a rapid response grant from the National Science Foundation, a research team from the University of Michigan and Stanford University is exploring this and other questions about how the novel coronavirus behaves and moves through the environment.

Krista Rule Wigginton

Project leader Krista Wigginton, an associate professor of civil and environmental engineering at U-M and currently a visiting professor at Stanford, has studied coronaviruses for the last several years. This family of viruses includes SARS, MERS and several strains of the common cold. Not much is known about their presence, persistence and transfer in the environment—both indoors and outdoors.

“One of the key areas we’re exploring is whether we can detect this new virus, SARS-CoV-2, in a community’s wastewater before it’s known to be circulating there,” Wigginton said. “The case numbers we’re seeing reported in the U.S. and lots of other places are dependent on how many test kits we have. So the curve displaying the number of cases is more of a curve of test kit availability in a community. What we see in wastewater may look totally different.”

It could perhaps provide a clearer picture of how broadly the disease is spreading because it could pick up evidence of upticks in more mild cases or those that bring no symptoms at all.

“For epidemiologists interested in the prevalence and incidence of COVID-19, our methodology offers an estimate that does not rely on testing every individual, nor is it as prone to measurement bias,” said Nasa Sinnott-Armstrong, a doctoral student at Stanford working on the project. “We could identify areas with rapidly increasing cases as a warning system to the health care system. Finally, these numbers can help epidemiologists model the trajectory of the pandemic with far less testing burden on our health care system.”

Going forward, if this pandemic continues in waves, wastewater sentinels could inform—before ICU admissions spike—when we need to head back indoors for another period of social distancing.

Alexandria Boehm

“Having a better way to know when social distancing is required would be helpful,” said Alexandria Boehm, professor of environmental engineering and the lead of the project at Stanford. “Our hope is that we can detect an uptick in cases with this tool faster than we can through clinical testing. We don’t know that for sure but that’s the hypothesis.

“It sounds to me like the earlier you halt the transmission in a community, the shorter periods of time you’ll need strict social distancing measures and the less inconvenient it will be for a community,” said Boehm, who is also a senior fellow at the Stanford Woods Institute for the Environment.

Sewage surveillance is already used in Israel to monitor poliovirus circulation. And in the case of COVID-19, the data could also provide insights into the diversity of viruses circulating in a community. (Wigginton is not concerned that SARS-CoV-2 would stay infective and elude wastewater treatment processes. Previous research with coronaviruses and other enveloped viruses, suggests the viruses are effectively removed with traditional water purification treatment steps.)

All of this is dependent on whether the team can detect it. Since early March, they’ve been gathering samples through the wastewater pathogen monitoring project at the Stanford Codiga Resource Recovery Center.

Craig Criddle

Led by Craig Criddle, professor of environmental engineering and science, it’s a pilot scale wastewater treatment plant that treats sewage from Stanford’s campus. The team also is sampling in several nearby municipalities including Santa Clara County, where two of the nation’s first cases of COVID-19 were reported. In the next few weeks, they’ll begin analyzing the samples.

Several other research groups are looking at wastewater as well but so far there are no reports of SARS-CoV-2 being detected. The U-M/Stanford team has an advantage in that Wigginton has previously published a study on recovering coronaviruses from wastewater.

“In addition to collecting wastewater influent samples and archiving them, we’re also grabbing primary solid samples,” Wigginton said. “Our previous work suggests that these viruses stick to wastewater solids more than other viruses. We’re hopeful that we’ll be able to detect something.”

The wastewater work is just one prong of the study. The researchers will also investigate:

How the virus responds to ultraviolet and solar light—a potential disinfectant.

How, and under what conditions like temperature and humidity, the virus transfers between fingers and inanimate objects. No work to date has looked into this process for “enveloped” viruses like coronaviruses and influenza, which are encased in a layer of lipids—organic compounds that aren’t soluble in water. This particular research question will likely need to wait until universities can safely lift the current restrictions on human subjects.

The project overall aims to close some critical gaps in our knowledge of enveloped viruses, and environmental engineers are uniquely suited for the job. While virologists typically focus on how viral pathogens behave in the body, environmental engineers explore their fate and detection in the environment, and understanding that can lead to insights that help limit spread. The researchers have also published a viewpoint in Environmental Science & Technology calling for a broader, long-term and more quantitative approach to understanding viruses, such as SARS-CoV-2, that are spread through the environment. Read a Q&A on the piece from Stanford News Service.